Such a mass flowmeter is known from U.S. Pat. No. 4,658,657.
The known mass flowmeter comprises a loop-shaped tube (half a turn) that forms a transverse branch at one side and two lateral branches clamped in at the opposite side in a mounting beam. The latter is mounted in a support such that it can rotate about a central axis lying in the plane of the loop. An electromagnetic excitation system cooperating with the mounting beam provides an oscillatory rotation (rotational vibration) of the mounting beam with the loop about the central axis. (The term ‘excitation’ is here understood to mean ‘causing to oscillate’).
When a medium (gas or liquid) flows through the loop that rotates about the central axis, Coriolis forces are generated in the transverse branch, resulting in an oscillation of the loop about a secondary axis. This oscillation, which is proportional to the flow, is superimposed on the fundamental oscillation and leads to a phase shift between the oscillations performed by the ends of the transverse branch. The phase difference is proportional to the Coriolis force and accordingly to the flow.
It is a disadvantage of the known system, however, that the mounting beam used for the excitation of the loop constitutes an additional mass. This prevents a change in the excitation frequency as a function of the density of the medium flowing through the tube, with the result that a measurement of the density (an additional property of a Coriolis flowmeter) becomes less accurate.